title: Calmodulin-regulated, ATP-driven calcium transport by basolateral membranes of rat small intestine.
abstract: Uptake of calcium by a membrane fraction enriched in basolateral plasma membrane vesicles from rat small intestine has been investigated using a rapid filtration technique. Calcium accumulation is stimulated by ATP and released by the calcium ionophore A23187. Kinetic studies indicate a calcium concentration of 28 nM for half-maximal stimulation of ATP-driven uptake. Transport is minimally inhibited by oligomycin and ouabain but is reduced 40% by lanthanum and abolished by 50 microM vanadate. The ATP-dependent calcium uptake is stimulated by the calcium regulatory protein, calmodulin, in a dose-dependent fashion. Calmodulin increases both the maximal transport rate and the calcium affinity of the transport mechanism. These results are consistent with the existence of an ATP-dependent, calmodulin-regulated calcium transport mechanism in the basolateral plasma membrane of intestinal epithelial cells, and suggests that calmodulin may modulate transepithelial calcium absorption in addition to controlling cytosolic calcium levels.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000494:pharmacology*; D002147:Calmodulin / Q000494:pharmacology*; D004848:Epithelium / Q000378:metabolism; D007421:Intestine, Small / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D009840:Oligomycins / Q000494:pharmacology; D010042:Ouabain / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D002135:Calcium-Binding Proteins; D002147:Calmodulin; D009840:Oligomycins; D000001:Calcimycin; D010042:Ouabain; D000255:Adenosine Triphosphate; D002118:Calcium